Blue circle and blue spot

These simulations show the relation of blue circle (from random crystals) and blue spot (from oriented crystals). Blue spot on parhelic circle occurs where blue circle crosses it. The blue circle itself has a radius of 64°, as Ágnes Kiricsi has pointed out, and it is centered around the subanthelic point. Sun elevations in the simulations are 10°, 20° and 31°. When sun is higher than 32°, blue spot is no more seen. Simulations are made with Jukka Ruoskanen’s software.

In the era of film cameras the broblem was that blue spot colors bleached in the film, although the colors were prominent with naked eye. The blue color was barely seen on film and green disappeared completely. Now with digital cameras and usm we should get better photos of blue spot, but… where are the good photos?

To my eyes the blue spot in that video is very clear, but sadly the quality of the video is too low for any still images to be extracted from it. But the blue spot should be there if the plate halo intensity is such as in the video.